Lecture 6 - Anatomy of neural circuits underlying behaviour

Question 1

In what three ways can you section the brain?

Answer 1

Coronal (like chopping cucumber)
Horizaontal (like cutting a roll open)
Sagittal (Straight down the middle lengthways)

Question 2

What structures is the CNS composed of?

Answer 2

Forebrain
-cerebral hemisphere/cerebrum
-Diencephalon 
Midbrain
Hindbrain
-Pons
-Cerebellum 
-Medulla
Spinal Cord

Question 3

Where are the more evolutionarily advanced structures of the brain located?

Answer 3

At the front of the brain

Question 4

How can you view the living human brain?

Answer 4

MRI scan

Question 5

How does an MRI scan work?

Answer 5

• nuclei of hydrogen atoms in H20 act as spinning magnets
• uses a very strong magnetic field to align protons
• a burst of radio waves temporarily flips the protons out of alignment and when the protons return to the aligned state they emit energy which can be detected
• hydrogen in different types of tissue (grey v white v CSF) has slightly different alignment rates

Question 6

What are the features of the brain stem?

Answer 6

Brain stem

• ancient part of the b rain
• composed of the midbrain, medulla and the pons
• site of entry for sensory information (touch, hearing, balance and taste)
• Mediates arousal by controlling cortical activity
• inv. in digestion respiration heart, rate, blood pressure and swallowing

Question 7

What are the features of the cerebellum?

Answer 7

Cerebellum

• inv. motor tasks
• recieves input on motor task to be performed and progress of ongoing task and provides the corrective signals to keep the task on target by defining fine movements
• inv. in learning of motor skills

Question 8

How is an fMRI different to an MRI scan?

Answer 8

functional MRI, views ‘active’ regions
imaging involved in brain metabolism
BOLD (blood oxygen level dependent)

Question 9

How does an fMRI work?

Answer 9

• Haemoglobin in the blood distorts magnetic resonance properties of nearby hydrogen atoms
• amount of disdstrotion is different in oxygenated and deoxygenated blood
• fMRI measures areas where there are higher levels of oxygenated blood in the brains, correlating with neuronal firing
• fMRI activity can be superimposed onto a MRI scan

Question 10

What is the cerebral hemispheres and what are the sections of the cerebral hemispheres?

Answer 10

-Heavily wrinkled outer layer of the brain, recieves a high level of input from the 4 lobes 
Frontal lobe
Parietal lobe
Occupital lobe
Temporal lobe

Question 11

What are the 4 lobes of the cerebal hemispheres involved in ?

Answer 11

Frontal lobe
-planning future actions (prefrontal cortex)
-control of movement (motor cortex)
Temporal lobe: hearing
-Deep-lying structures ( for learning and memory (hippocampous) 
Occipial lobe
-vision 
Parietal lobe
-somatic sensation, from skin and touch

Question 12

How is the cerebral cortex organised?

Answer 12

Into cell layers which organise inputs and outputs

Different in different layers, e.g. visual cortex more dense layers than the motor cortex [?]

Question 13

What is an emotional state made up of, explain with fear as an example

Answer 13

• Physical sensation (increased heart rate and sweating)

- Conscious feeling (subjective, conciously feel afraid)

Question 14

What is involved in the physical sensation of emotional states and what subcortical structures controls these?

Answer 14

Involves the peripheral, autonomic, endocrine and skeletomotor responses
Subcortal structures: Amygdala, hypothalamus and brain stem

Question 15

What is involved in the conscious feeling of an emotional state?

Answer 15

Cortical structures
(orbital and medial frontal lobes, prefrontal cortex)

Question 16

Why is it important to investigate emotional reponses?

Answer 16

Because emotions influence motivational behaviour

Question 17

What is the Amygdala required for?

Answer 17

experiencing both fearful and pleasurable responses and is required for generating memories associated with emotional experience

Question 18

How was fear conditioning shown experimentally in rats and what did this show?

Answer 18

1. Rats were placed in a cage and exposed initally to a neutral stimulus, to which they showed no response
2. They were exposed to a aversive foot shock, which exhibited an increase in blood pressure and freezing response
3. When the neutral stimulus was paired with the aversive foot shock they learned to associate the neutral stimulus with the foot shock and when the neutral stimulus was applied after this the rats showed a learned response
4. However rats with lesions in the amygdala lack the conditioned response
   SHOWED: the physical expression of fear is orchestrated by projections of the amygdala to the hypothalamus and brain stem

Question 19

What was shown by the patient S.M?

Answer 19

S.M: damaged amygdala but intact hippocampus-explicit memory

-tested for her ability to rate the intensity of human facial expressions of happiness, surpise, disgust, fear, anger and sadness

Failed to recognise fear when compared to control patients
Amgdala involved in the fear response in human

Question 20

How were the distinctive roles of the amygdala and hippocampus shown experimentally?

Answer 20

3 individuals with selective damage to different brain regions were shown different coloured slides and some colours were followed by a loud startliing noise
-their autonomoic responses were measurede

1- with no lesions in the brain, patients showed a concious memory of the colour and a learned fear of the colours
2-with lesions in the amygdala, patients shown a conscious memory of the colours but no learned fear of the colours
3 - with lesions in the hippocampus patients showed no conscious memory of seeing the colours but a learned fear response to the colours
4 - with lesions in both, patients showed no conscious memory of colours and no learned fear

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Question 21

How was it shown that explicit conscious processes are involved to implement motivational behaviour in rats?

Answer 21

• cage was divided into 2
• in one half of the cage there was food/foot shock and in the other there was nothing
• when replaced into the cage, rats immediately returned to the side with food/ without foot shock

Illustrated the processes in the brain involved in associative learning in the amygdala

Question 22

What is the brain process of associative learning in the amygdala? [rat experiment]

Answer 22

1 - the primary reinforcer (pain, e.g. foot shock) are recieved from the sensory cortex alongside the neutral sensory stimuli
2- the amygdala has connections with the hippocampus to record a memory of the experience and the context
3- outputs are sent through the:
-orbital and medial prefrontal cortex - involved in the conscious processing to implement reqard seeking behaviour and avoid punishments
-Hypothalamus and brain stem - involved in visceral motor effector systems e.g. freezing and increase in blood pressure

Question 23

What is another name for the reward circuit?

Answer 23

The Mesolimbic Dopamine System

Question 24

What are the two states driven by motivation and reward? (also anticipatory mechanisms, next lecture)

Answer 24

1- Drive states directed towards maintaining physiological homeostasis
-such as feeding behaviour/appetite
-controlled in part by the hypothalamus - hypothalamic neurons have receptors for the hormone leptin (produced by fat tissue) that supresses appetite and stimulates metabolic rate
2-Motivational states driven by reward/pleasaurable and reinforcing effects of a stimulus
-feeding behaviour, tend to eat more palatable than bland food

Question 25

Ouline the Mesolimbic dopamine system (the reward circuit

Answer 25

1-Stimuli signal the presence or prospect of reward/pleasure by activating midbrain dopamenergic neurons in the ventral temental area that project to the nucleaus accumbens region of the forebrain

Question 26

How is the level of signalling in the reward circuit from the midbrain dopaminergic neurons to the Nuc Acc in the forebrain important?

Answer 26

The level of signalling equates to the level of pleaseure of the reward

Question 27

How was it shown that the activation of the Nuc Acc predicts reward value?

Answer 27

• participants listened to previously inheard music excerpts whilst undergoing MRI scanning
• the reward value was asses by asking participant to bid on music with their own money (0-$2)
• activity in the nucleus accumbens correlated with higher bids

Question 28

What are the neural circuits underlying emotional responses and rewards?

Answer 28

Ventral tegmetnal area (VTA) and the nucleus accumbens
-assigns reqard value ‘rheostats’ of reqard - how rewarding is it
Amygdala (and hypothalamus)
-amygdala assigns an emotion to a stimuli
-makes connection between experience and other cues
-direct autonomic responses via hypothalamus
Hippocampus
-records memory of experience and context
Frontal regions of the cortex
-process and coordinate information and determine conscious behaviour to obtain reward and avoid punishment